The invention relates generally to hydrocutting of food, and more particularly to a method and apparatus for maintaining constant acceleration of food products in a hydrocutting system.
Many food products, particularly vegetables and fruits, are processed prior to sale to preserve the food so it is safe and appealing at the time of consumption. The processing can be by canning or freezing, among others. Furthermore, unless it is an edible size before processing, most food products must be sliced or otherwise shaped into an edible size prior to the preservation process. Slicing and shaping operations have been accomplished traditionally with sharpened blades. Such blades can be hand-held, but hand-held knives are relatively slow and dangerous to the person using them. Other blades are machine-driven and other machines for cutting drive the food products at high speed into a stationary or machine-driven blade. Food cutting machines increase the rate and consistency of slicing, and provide a higher degree of safety in the food slicing industry.
Recent advances in food product cutting technologies have resulted in the hydraulically fed cutting apparatus. The driving force used in this system is moving water, and thus the process is called “hydraulic cutting”, which is referred to by the shorthand term “hydro-cutting”. Hydrocutting involves the propulsion of water and food products, typically at very high speed, through a path that includes a stationary cutting blade. In the vegetable and fruit cutting industry, food products are sliced along the longitudinal axis (e.g., French fries) and along the transverse axis (e.g., potato chips). Production cutting systems and related knife fixtures are generally well known in the art of hydrocutting vegetable products. Typical hydrocutting systems have a knife fixture that is mounted at a position along the path of the food product to slice parallel to the flow of water. Such parallel cutters usually cut or slice into strips or, with added motions, into a helical shape. In such a system, the food products are conveyed one-at-a-time in single file succession into the stationary cutting blades with enough kinetic energy to carry the product through the stationary knife fixture.
Hydraulic food cutters are used to cut a wide variety of food products, including potatoes, carrots, beets, zucchini, cucumbers, and others. Cutting potatoes has been the most common application of hydrocutting machines. However, it should be understood that these hydraulic food cutters are capable of cutting, and are used to cut, a wide variety of food products.
The basic configuration of a prior art hydrocutting system is shown, in schematic format, in FIG. 1. In such a typical prior art hydraulic cutting apparatus, where potatoes are to be cut, the potatoes are dropped into a tank 10 filled with water and then pumped through conduit into an alignment chute or tube 12 wherein the potatoes are aligned and accelerated to high speed before impinging upon a fixed array of cutter blades where the potato is cut into a plurality of smaller pieces.
The tank filled with water, which is one of the components of a prior art hydraulic cutting apparatus for use in cutting potatoes, is referred to as a receiving tank 10. Peeled or unpeeled potatoes are dropped into the receiving tank and a food pump 13, typically a single impeller centrifugal pump, is provided to drive the potatoes through the system. The pump draws water from the receiving tank and pumps the water and the suspended potatoes from the tank into the accelerator tube 12, which functions as the converging portion of a venturi. The accelerator tube is used to accelerate, singulate, and align the potatoes immediately prior to impinging upon the stationary knife blades of the cutter blade assembly 14.
The use of an accelerator tube is required in order to perform at least three functions. First, the accelerator tube accelerates the water and food product to the velocity required in order for it to pass cleanly through the knife blade assembly. Second, the accelerator tube aligns and centers the food products prior to impingement upon the knife blade assembly. In the case of potatoes, a common velocity range is from about 40 to about 60 feet per second. Third, the acceleration of the product causes multiple products to separate while aligning them, thereby causing them to enter the cutter in a single file line.
Potatoes can be cut into French fry sticks as one example of the use of hydrocutting systems, and will be used as an example hereafter. A person of ordinary skill will understand, after reading the description herein, how to adapt the apparatus described herein to other food products. Each whole potato impinging upon the knife blade assembly at high speed passes through the cutting blade array and is thereby cut into a plurality of food pieces, for example French fry pieces. The cross section of each of the food strips is determined by the arrangement of the cutter head knives.
A portion of the hydrocutting system separates the food product strips from the water once the strips are past the cutter head. It is desirable to slow down the water column and the food product strips within it in a controlled manner before this separation portion is encountered. This is because the strips may be fragile (depending on the food product) and gentle handling in the sections following cutting prevents breakage of, or stress on, the strips that would render the strips less desirable. The food strip pieces thus pass with the water into the second half of the venturi which is a diverging tube 15 in which the water and the cut food pieces are decelerated back to a slower velocity. The water and cut food pieces are then deposited onto a dewatering conveyer 16. The water passes through the dewatering conveyor and is collected and recycled back to the receiving tank. The cut food pieces remain on the conveyor and are carried off for further processing.
During the cutting process, as the potato approaches the cutting knives, the potato needs to be aligned and stabilized with the central axis of the knife set. This alignment maximizes finished product yield. In the past, significant effort has been directed toward the development of good alignment or acceleration tubes that can properly align and accelerate the whole food product so that each whole food product is properly centered relative to the cutter blade array prior to impinging upon it. An example of these efforts can be seen in U.S. Pat. No. 4,614,141, which teaches an alignment tube assembly used to accelerate and align whole potatoes immediately prior to impinging upon a cutter head array. Other patents of interest include U.S. Pat. No. 5,568,755 and U.S. Pat. No. 5,806,397, both of which, along with U.S. Pat. No. 4,614,141, are hereby incorporated by reference.
As noted above, the water and the food product are pumped through a decreasing diameter accelerating section conduit in order to increase the speed of the food products and water as they approach the blade. Unless otherwise specified, the term “acceleration” and its derivatives are used herein to denote both positive and negative (increasing and decreasing) changes of velocity per unit time. While the water and food products increase in speed through the accelerating section, the individual items in the stream made up of water and multiple food products also orient and align for cutting as they pass through the cutter head. The accelerating section also singulates the food products, meaning the food products travelling through conduit laterally beside one another are arranged in a “single file” line before each item passes through the cutter head. As shown in FIG. 1, the cutter head is in a specific section that is removable for service, change of cutting pattern and/or replacement.
In conventional hydrocutting art there are two or three conically-shaped accelerating sections that have specified angles and transitions that are used in an attempt to optimize the acceleration of the potatoes into and out of the cutting head. Similarly, the art describes specific diverging angles that attempt to controllably slow the water flow in the accelerating section of the system that can be referred to as the “exit section” (or “decelerating section”). In every case known to the inventors, the prior art devices accomplish the goal of accelerating (entry or exit sections) using linear changes of cross section over the length of the accelerating section. Sometimes two or three sections are combined in which each section has a specific angle associated with it that results in a changing acceleration through that section.
The need exists for an accelerator tube that has a superior effect on the food products as they are being accelerated just before and/or just after being cut by the blades.